1. Field of the Invention
This invention relates to the retroreflective roadway markers that are used for traffic lane delineation and in particular, to markers with enhanced reflectivity and abrasion resistant.
2. Related Art
Roadway markers are adhered to pavements along centerlines, edge lines, lane dividers or guardrail delineators. Other roadway markers are used as temporary lane dividers in temporary constructions, detours or prior to permanent marking of newly paved roadways.
Since 1965, the most commonly used retroreflective roadway markers are based on Heenan U.S. Pat. No. 3,332,327 or Balint U.S. Pat. No. 3,409,344.
Typically, this type of markers are produced in a process consisting of four to five steps:
First, injection molding of a thermoplastic shell, either integrally molded with the reflective face, or the reflective faces welded on a corresponding open recesses within the shell. The reflective face, having 350 or more cube corner reflective elements on each reflective face of the shell.
Secondly, either the cube corner reflective elements within a shell or the entire inside surface of the shell coated with a reflective sealer by a process known as vacuum in metalizing. This metallic sealer needed to seal the cube comer reflective elements so they retain part of their retroreflectivness prior to the next step, of filling the shell with a thermosetting resinous material, such as epoxy or polyurethane. This resinous filler material encapsulate the metalized cube corner reflective elements and give the marker the structural body.
Finally, a layer of relatively course sand or glass beads dispersed over the top surface of the filler material (this top surface will be the marker""s base) prior to solidification of the filler material. Part of the sand particles will remain partially protruding above this planar surface of the marker base, thereby increase the adhesive welding parameter of the base surface. This will improve adhesion to substrate, regardless of the type of adhesive used. This type of markers worked well for six or seven months, however, due to poor abrasion and impact resistant of the thermoplastic shell, nearly 60% of the reflectivity is lost thereafter. Also, incompatibility of the shell material to the resinous filler material, causes pealing of the reflective face or the shell, thereby losing retroreflectivity. Several attempt were made to improve abrasion resistant of the reflective face. One was the use of thin layer of untempered glass as disclosed in U.S. Pat. No. 4,340,319. Another attempt was the use of polymeric coating of the reflective face, as disclosed in U.S. Pat. No. 4,753,548 (Forrer). These abrasion resistant coating proving to be expensive and tend to reduce retroreflectivity.
Other major development in the pavement marker art have been made in the attempt to eliminate the use of the metalized sealer for the cube corner reflective elements. This has been achieved by dividing the inside surface of the reflective face into reflective cells, each cell will have several cube corner reflective elements, the cells isolated from each other by partition and load carrying walls. The entire reflective face welded to corresponding recesses within a hollowed body.
This method is disclosed in U.S. Pat. No. 4,227,772 (Heenan); U.S. Pat. Nos. 4,232,979; and 4,340,319 (Johnson et al); U.S. Pat. No. 4,498,733 (Flanagan). These markers proved to be superior in reflectivity, however, lack of structural strength and poor adhesion cause short life cycle for this type of markers.
This applicant successfully developed two multi-cell reflective roadway markers. One roadway marker utilizes raised rhombic shaped abrasion reducing and load transferring raised ridges which act to intercede abrasion elements and impact load, the shell filled with epoxy, the marker body having a base with large wetting parameter for shear and flexural strength , as disclosed in U.S. Pat. No. 4,726,706. The second roadway marker of this applicant, U.S. Pat. No. 5,927,897 developed a mean to increase the abrasion resistant of the reflective face by coating the reflective face with diamond-like film and by having holding pins extending from the partition walls into the body, the holding pins sealed by the filler material; this works very effectively. All of the above reflective pavement markers are incorporated herein by reference in their entireties. Applicant present goal to have a roadway marker with high reflectance, abrasion resistant, low cost, marker base area with good welding parameter and very simple yet consistent process to manufacture.
This invention provide a novel one piece raised roadway marker that comprises a monolithically injected body, together with one or two reflective faces and a base having large adhesive welding parameter for better adhesion to the pavement and higher resistance to flexural stresses .
The primary object of this invention is eliminate the multi steps process in prior arts for making reflective and non-reflective pavement markers while retaining maximum base surface area. Another objective of this invention is to provide a raised roadway marker made of high impact and abrasion resistant material with high impact resistance and good quality reflective index.
The present invention further provide a method of making one piece raised roadway marker of any desirable shape and configuration such as a marker with truncated body or one piece marker with a body having two rumble portions integrally made with two reflective faces and scalloped recess in-between with rectangular textured base.
In accordance with still further aspect of this invention, the marker can be made for one or two way traffic usage, having integrally built-in reflective faces, this will cost considerably less to install to the roadway, or two multi colored parts can be welded together, each with one reflective face opposite the other.